OFF THE SHORE OF OAHU — It was only when the sharks had a momentary feeding frenzy 6 feet from me that the wondrous beauty of Hawaiian nature was eclipsed by a “what the hell am I doing here?” moment.

I had surfaced, and so had two big 9-footers, and all that separated us was the top couple bars of the shark cage in which I treaded water.

The sharks thrashed. Saltwater splashed. I looked at the metal bars, rising just a foot or so above the surface, and the question arose: Are sharks good jumpers?

I was about three miles off Oahu’s North Shore on a “shark encounter” outing aboard the good ship Kainani. Well, I wasn’t exactly “aboard” at the moment — I was with two other tourists from the mainland (call them my encounter group) splashing about inside an open-topped, 8-foot-square cage held up by balloon-shaped floats and tethered about 10 feet from the boat.

We’d motored 20 minutes out of Haleiwa Harbor. In the light of dawn, windblown rollers kept the boat — and our masked, snorkel-spiked heads — bobbing. Beneath us was 800 feet of the most blueberry-colored water I’d seen outside of Crater Lake.

My wife had found this adventure online and emailed me the link as a joke. She didn’t think I was this dumb; I signed right up. The outfitter highly recommended the day’s first outing, 6:30 a.m., for the calmest waters, so there I was.

The rain had stopped and the rising sun peeked from behind billowing clouds as we bounced our way seaward in the 25-foot Kainani. Ours wasn’t the first shark boat to leave the harbor.

“We saw that other boat pulling out, and we thought it was ours, and my daughter said, ‘Maybe we’re just not meant to go on this!’ ” said fellow passenger Carla Creameans, from San Diego, who quickly professed to our skipper, Rich Whyte, that she’d been up late partying and was feeling a little delicate.

“You want slow and bumpy or fast and bumpy?” Whyte grinned. We’d been warned that seasickness was a hazard on this outing.

We’d just signed the most detailed and graphic legal waiver I’d ever seen, acknowledging that messing about in a shark cage can result not only in physical injury or death — the obvious things — but in “serious emotional injury.”

That was food for thought during the ride out.

The chumming question

Before signing up, I did a little checking. On its website, my chosen outfitter painted itself as dedicated to environmental education and teaching clients about sharks.

While there are clear advantages to having an informed public with firsthand knowledge of the beauty of nature, as is sometimes the case with “eco-adventures” there was an ethical question. Here, it was whether they drop food overboard — chum the waters — to attract sharks.

Not only did I not wish to swim among bloody fish entrails, such activity can modify the behavior of wild animals and affect their ability to survive on their own. (It’s the same reason you see “don’t feed the ducks” signs in parks.) For such reasons, state and federal regulations prohibit feeding sharks in Hawaii.

I contacted the company up front. They assured me by email that they don’t feed sharks.

So why do sharks come to their boats?

For years, crabbers and fishermen have thrown fish waste off boats out here, “so these sharks are accustomed to being fed off boats,” explained Phil Oury, Kainani’s young crewman.

“And don’t tell the competition, but we have the same engine as the crabber, so the sound is the same,” Whyte added. “It’s like the ice-cream truck!”

He advised our group to watch for tagged sharks, an indication they have a transmitter in their belly, part of a University of Hawaii study in which his company has taken part.

Into the cage

We soon arrived at the shark cage, which our crew had brought out and tethered to a mooring at first light. After a few instructions, during which she looked almost as green as distant Kaena Point, Creameans was first into the cage. She splashed, ducked under, then quickly surfaced and called out, “They’re here!”

Whyte grinned and mimicked her words. ” ‘They’re here!’ Isn’t that like what they said in ‘Jaws’ or something?”

These typically are sandbar sharks and larger, 8- to 9- foot Galapagos sharks, Oury said. “They’re a very bold shark, not afraid to come up to the boat. But in all our experience over the years, they’re really docile animals.”

For what is billed as an educational experience, there wasn’t a lot more educational talk, though the crew was happy to answer questions.

Once in the water, I ducked my mask under and there they were, indeed: battleship gray, six or eight or more at a time, circling the cage and the boat. Big dorsals, like ax heads, and long, dagger-pointed tail fins slicing the sea.

They glided without apparent effort, studies in streamlining, against an endless backdrop of blue water. I couldn’t stop looking. I took big gulps of air and dived toward the bottom of the cage, where the water was calm and quiet. Some came nosing up curiously. I felt awed, not threatened.

Oury had loaned me his underwater camera, a soap-bar sized GoPro Hero. In about 20 minutes I shot more than 70 photos, sometimes daring to stick my hand out through the cage. But not for long.

We saw one tagged shark. Another had a fishing hook embedded in its snout.

Back on the boat, a warm shower from a spray nozzle felt great, though I really hadn’t gotten cold in the tropical water, even without a wet suit like my cohorts wore.

“That was awesome,” said Jessica Creameans, the San Diego daughter.

I asked about the little feeding frenzy. Oury said he had dumped some old tuna. I had noticed some white flecks in the water. It wasn’t a lot but it was food the sharks liked.

So maybe as a policy they don’t feed the sharks, but this day sharks got a little treat. Draw your own conclusion.

The real “Jaws” moment was when I was catching my breath at the water’s surface, looking out from the cage, and saw a high dorsal fin break the water and dart quickly toward me.

The reaction was visceral. It was like looking up railroad tracks at a locomotive’s headlight and I was driving the stalled car. Cue the scary music: